Overview

Brief Summary

The red kangaroo (Macropus rufus) is the largest of all kangaroos, the largest mammal native to Australia, and the largest extant marsupial. It is found across mainland Australia, avoiding only the more fertile areas in the south, the east coast, and the northern rainforests. Th red kangeroo has long, pointed ears and a squared-off muzzle. Males have short, red-brown fur, fading to pale buff below and on the limbs. Females are smaller than males and are blue-grey with a brown tinge, pale grey below, although arid zone females are coloured more like males. It has two forelimbs with small claws, two muscular hind-limbs, which are used for jumping, and a strong tail which is often used to create a tripod when standing upright.

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Physical Description

Morphology

Macropus rufus is the largest living marsupial. Males range in total body length from 1,300 to 1,600 mm and females from 850 to 1,050 mm. Tail length is from 1,000 to 1,200 mm for males and 650 to 850 mm for females. They may weigh as much as 90 kg and may reach 1.8 meters in height when standing. Coat color is usually reddish brown in males and bluish gray in females, although these colors are reversed in some areas, with females being reddish and males blue-gray. Red kangaroos are robustly built, with large, well-muscled tails and powerful hindquarters. The tail is strong enough to support the kangaroo's body weight, acts as a balance when jumping, and is used, with the two legs, to form a tripod for resting. The second and third toes of red kangaroos are fused and shaped into a grooming claw. Their foreshortened upper limbs terminate in clawed paws used with great dexterity in eating, grooming, and self-defense. Females have a forward facing pouch and 4 mammae.

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Ecology

Habitat

Red kangaroos live over most of the central part of Australia in areas where rainfall averages less than 500 millimeters. They prefer to forage in open plains habitats with neither trees nor bushes, but are seldom found in regions without shade and shelter from scattered trees.

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Habitat and Ecology

It is found in arid and semi arid habitats. Animals are dependant on green herbage, and populations subsequently decline during drought periods (Croft and Clancy 2008). It is capable of traveling long distances (over 200 km) in response to localized rainfall.

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Trophic Strategy

Red kangaroos are exclusively plant-eaters, with a preferred diet of green herbage including grasses and dicotyledonous flowering plants. These herbivores can go without water for long periods of time by consuming moisture-filled succulent plants.

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Their large size reduces the predation risks faced by red kangaroos. Very young joeys are protected in their mother's pouch and red kangaroos can use their robust legs and clawed feet to defend themselves from attackers with kicks and blows. They may be preyed on by dingos and very young joeys, just out of the pouch, may be taken by large raptors. Humans have historically hunted kangaroos for their meat and hides and human hunting continues to be the primary source of predation for red kangaroos.

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Life History and Behavior

Behavior

Little information on communication among red kangaroos is available. Like most mammals, red kangaroos are likely to make extensive use of chemical modes of perception and communication. They also have excellent vision and hearing, suggesting these are important sensory modes.

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Lifespan, longevity, and ageing

Maximum longevity: 25 years (captivity) Observations: In the wild, these animals have been estimated to live up to 27 years (Ronald Nowak 1999), which is plausible but unverified. There are also anecdotal reports of animals living more than 30 years. These animals are common in zoos, however, and record longevity in captivity is only 25 years (Richard Weigl 2005).

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Reproduction

Male red kangaroos compete for mating opportunities with several females. Males will try to monopolize access to several females and will actively drive away other males. This competition sometimes leads to "boxing" matches, where males hit at each other with their forepaws and kick with their feet. There is no permanent association of males and females.

Mating System: polygynous

Macropus rufus has a short gestation period. The young are born 33 days after mating, and mating can occur again a day or two after parturition. The fertilized egg resulting from this post-partum mating develops only to the blastocyst stage and then undergoes a period of embryonic diapause. Development is resumed if the previous young, which is still suckling in the pouch, reaches 204 days old or if it dies or is removed. Young kangaroos are known as joeys. Red kangaroo joeys are tiny when born, averaging only 2.5 centimeters long and 0.75 grams. After the joey is born, it crawls up the mother's fur, into her pouch and immediately attaches itself to a nipple. During this period, the sucking stimulus prevents the re-occurence of fertility cycles. Given favorable conditions, a mother red kangaroo produces and raises an average of three young every two years. Individual females often have, simultaneously, a joey outside of the pouch, a joey in the pouch, and a blastocyst awaiting implantation. Compared to the gestation period, the period of lactation is long, about one year in red kangaroos.

A mature female red kangaroo which is appropriately nourished, and which is not suckling a young in its pouch already, becomes fertile at approximately 35 day intervals and is, like the male, potentially fertile throughout the year. Unlike the suckling period, pregnancy does not interrupt recurrence of fertility.

Sexual maturity is reached at 15 to 20 months in females and 20 to 24 months in males, but maturity may be delayed in unfavorable conditions.

Breeding interval: Given favorable conditions, a mother red kangaroo produces and raises an average of three young every two years.

Breeding season: Red kangaroos can breed throughout the year.

Range number of offspring: 2 (high) .

Average number of offspring: 1.

Average gestation period: 33 days.

Average weaning age: 12 months.

Range age at sexual or reproductive maturity (female): 15 to 20 months.

Red kangaroo young are tiny when born and make their own way from the birth canal to the pouch and a nipple to which they permanently attach themselves for about 70 days. They are born with well-developed tongues, jaw muscles, nostrils, forelimbs, and digits. Otherwise their external features are embryonic. Females lactate their young for about a year and carry them in their pouch for about 235 days.

"Red kangaroos have excellent thermoregulatory abilities: evaporative heat loss mechanisms such as panting, sweating, and licking (Dawson 1973, 1989; Dawson et al. 1974; Needham et al. 1974) enable them to cope with high externally (Dawson 1972) and internally produced (Kram and Dawson 1998) heat loads. While the evaporative heat loss mechanisms utilised by red kangaroos have been suggested to follow an efficient pattern, we do not know the relative contribution of these mechanisms at high environmental temperatures. In regard to the grey kangaroos, little has been reported except that they pant and lick. Licking has been suggested to be the grey kangaroo’s major route of evaporative heat loss (EHL) at high temperatures (Robertson and Morrison 1957)." (Dawson et al. 2000:374)

"Cutaneous evaporation includes water loss through the skin (passive diffusion and sweating) and water spread onto the skin (licking)…Kangaroos and some wallabies have a special anastomosing network of superficial vessels in their forelegs to facilitate heat loss via licking (Needham et al. 1974), and this is most developed in M. [Macropus] rufus (Needham 1982). Large increases in foreleg blood flow occur in M. rufus when Ta [air temperature] is raised above thermoneutral levels (Needham et al. 1974; Needham and Dawson 1984). While circumstantial, the data suggest that licking provides most of the nonrespiratory EHL [evaporative heat loss] of M. rufus at 45°C." (Dawson et al. 2000:380)Learn more about this functional adaptation.

"One to three days after giving birth, a female kangaroo often mates again and another fertilized egg settles into her uterus…The fate of the egg…depends on what happens to [the first] baby. If the recently born baby has reached the pouch and latched onto a teat, the newly fertilized egg develops only to the blastocyst stage (about seventy to one hundred cells) and then stays in developmental dormancy until it receives the signal to continue to development. The blastocyst can remain dormant in the uterus for several months. If the newborn baby hasn't made it to the pouch or if it dies while in the pouch, the female's body releases a pulse of the hormone progesterone. This signals the blastocyst to continue to develop, and about thirty-three days later the 'replacement baby' will be born. The same happens once a mature joey is about to leave the pouch permanently and is nursing less: the mother's hormones kick in and the fertilized egg begins to develop." (Crump 2005:56)Learn more about this functional adaptation.

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Conservation

Conservation Status

Macropus rufus is not considered endangered. Nearly 3 million square miles of Australian territory now lies within the boundaries of excellent national parks. All Australian states regulate the hunting of kangaroos.

Listed as Least Concern in view of its wide distribution, presumed large population, occurrence in a number of protected areas, lack of major threats, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.

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Trends

Population

It is an abundant species (Croft and Clancy 2008) that is subject to commercial take under nationally approved management plans. Its abundance is limited by dingo predation, hence it is generally greater in abundance south of the dog fence or within dingo controlled zones. The species has benefited from pastoral infrastructure (i.e., artificial water sources).

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Wikipedia

Red kangaroo

The red kangaroo (Macropus rufus) is the largest of all kangaroos, the largest terrestrial mammal native to Australia, and the largest extant marsupial. It is found across mainland Australia, avoiding only the more fertile areas in the south, the east coast, and the northern rainforests.

Contents

This species is a very large kangaroo with long, pointed ears and a squared-off muzzle. Males have short, red-brown fur, fading to pale buff below and on the limbs. Females are smaller than males and are blue-grey with a brown tinge, pale grey below, although arid zone females are coloured more like males. It has two forelimbs with small claws, two muscular hind-limbs, which are used for jumping, and a strong tail which is often used to create a tripod when standing upright.

The red kangaroo's legs work much like a rubber band, with the Achilles tendon stretching as the animal comes down, then releasing its energy to propel the animal up and forward, enabling the characteristic bouncing locomotion. The males can leap 8–9 m (26.2–29.5 ft) long and 1.8–3 m (5.9–9.8 ft) tall in one leap, though the average is 1.2–1.9 m (3.9–6.2 ft)[3][4][5]

Males grow up to a head-and-body length of 1.3–1.6 m (4.3–5.2 ft) with a tail that adds a further 1–1.2 m (3.3–3.9 ft) to the total length. Females are considerably smaller, with a head-and-body length of 85–105 cm (33–41 in) and tail length of 65–85 cm (26–33 in).[6][7] Females can weigh from 18 to 40 kg (40 to 88 lb), while males typically weigh around twice as much at 55 to 90 kg (121 to 198 lb).[7][8] The average red kangaroo stands approximately 1.5 m (4.9 ft) tall to the top of the head in upright posture.[9] Large mature males can stand more than 1.8 m (5.9 ft) tall, with the largest confirmed one having been around 2.1 m (6.9 ft) tall and weighed 91 kg (201 lb).[8] Accounts of sizes greater than this are not uncommon, with some reportedly reaching a weight of approximately 150 kg (330 lb).[10]

The red kangaroo maintains its internal temperature at a point of homeostasis about 36 °C (97 °F) using a variety of physical, physiological, and behavioural adaptations. These include having an insulating layer of fur, being less active and staying in the shade when temperatures are high, panting, sweating, and licking its forelimbs.

The red kangaroo's range of vision is approximately 300°, due to the position of its eyes.[citation needed]

The red kangaroo ranges throughout western and central Australia. Its range encompasses scrubland, grassland, and desert habitats. It typically inhabits open habitats with some trees for shade.[11] Red kangaroos are capable of conserving enough water and selecting enough fresh vegetation to survive in an arid environment. The kangaroo’s kidneys are also great at concentrating urine, particularly during summer.[12] Red kangaroo primarily eat green vegetation, particularly fresh grasses and forbs, and can get enough even when most plants look brown and dry.[13] One study of kangaroos in Central Australia found that green grass makes up 75–95% the diet, with Eragrostis setifolia dominating at 54%. This grass continues to be green into the dry season.[14] Kangaroos also primarily consumed this species, along with Enneapogon avanaceus, in western New South Wales where they comprised much as 21–69% of its diet according to a study.[15] During dry times, kangaroos search for green plants by staying on open grassland and near watercourses.[13] While grasses and forbs are preferred, red kangaroos will also eat certain species of chenopods, like Bassia diacantha and Maireana pyramidata, and will even browse shrubs when its favoured foods are scarce.[13] However, some perennial chenopods, such as round-leaf chenopod Kochia are avoided even when abundant.[16]

At times, red kangaroos congregate in large numbers; in areas with much forage, these groups can number as much as 1,500 individuals. Red kangaroos are mostly crepuscular and nocturnal, resting in the shade during the day.[17] However, they sometimes move about during the day. Red kangaroos rely on small saltbushes or mulga bushes for shelter in extreme heat rather than rocky outcrops or caves.[13] Grazing takes up most of their daily activities. Like most kangaroo species, they are mostly sedentary, staying within a relatively well-defined home range. However, great environmental changes can cause them to travel great distances.[13] Kangaroos in New South Wales have weekly home ranges of 258–560 ha, with the larger areas belonging to adult males.[18] When forage is poor and rainfall patchy, kangaroos will travel 25–30 km to more favourable feeding grounds.[15] Another study of kangaroos in central Australia found that most of them stay close to remaining vegetation but disperse to find fresh plants after it rains.[19] The red kangaroo is too big to be subject to significant non-human predation. They can use their robust legs and clawed feet to defend themselves from attackers with kicks and blows. However, dingoes and eagles will kill and eat joeys. Joeys are thus protected in their mother's pouch. The red kangaroo formerly did have major predators that are now extinct. Extinct predators included the marsupial lion, megalania, and the wonambi. Kangaroos are adept swimmers, and often flee into waterways if threatened by a predator. If pursued into the water, a kangaroo may use its forepaws to hold the predator underwater so as to drown it.[20]

Red kangaroos live in groups of 2–4 members. The most common groups are females and their young.[13] Larger groups can be found in densely populated areas and females are usually with a male.[21] Membership of these groups is very flexible, and males (boomers) are not territorial, fighting only over females (flyers) that come into heat. Males develop proportionately much larger shoulders and arms than females.[22] Most agonistic interactions occur between young males, which engage in ritualised fighting known as boxing. They usually stand up on their hind limbs and attempt to push their opponent off balance by jabbing him or locking forearms. If the fight escalates, they will begin to kick each other. Using their tail to support their weight, they deliver kicks with their powerful hind legs. Compared to other kangaroo species, fights between red kangaroo males tend to involve more wrestling.[23] Fights establish dominance relationships among males, and determine who gets access to estrous females.[13] Alpha males make agonistic behaviours and more sexual behaviours until they are overthrown. Displaced males live alone and avoid close contact with others.[13]

The red kangaroo breeds all year round. The females have the unusual ability to delay birth of their baby until their previous Joey has left the pouch. This is called embryonic diapause. Copulation may last 25 minutes.[23] The red kangaroo has the typical reproductive system of a kangaroo. The neonate emerges after only 33 days. Usually only one young is born at a time. It is blind, hairless, and only a few centimetres long. Its hind legs are mere stumps; it instead uses its more developed forelegs to climb its way through the thick fur on its mother's abdomen into the pouch, which takes about three to five minutes. Once in the pouch, it fastens onto one of the two teats and starts to feed. Almost immediately, the mother's sexual cycle starts again. Another egg descends into the uterus and she becomes sexually receptive. Then, if she mates and a second egg is fertilised, its development is temporarily halted. Meanwhile, the neonate in the pouch grows rapidly. After approximately 190 days, the baby (called a joey) is sufficiently large and developed to make its full emergence out of the pouch, after sticking its head out for a few weeks until it eventually feels safe enough to fully emerge. From then on, it spends increasing time in the outside world and eventually, after around 235 days, it leaves the pouch for the last time.[24] While the young joey will permanently leave the pouch at around 235 days old, it will continue to suckle until it reaches about 12 months of age. A doe may first reproduce as early as 18 months of age and as late as five years during drought, but normally she is two and a half years old before she begins to breed.[25]

The female kangaroo is usually permanently pregnant, except on the day she gives birth; however, she has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch. This is known as diapause, and will occur in times of drought and in areas with poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. In addition, red kangaroo mothers may "have up to three generations of offspring simultaneously; a young-at-foot suckling from an elongated teat, a young in the pouch attached to a second teat and a blastula in arrested development in the uterus".[23]

The kangaroo has also been observed to engage in alloparental care, a behavior in which a female may adopt another females joey. This is a common parenting behavior seen in many other animal species like wolves, elephants and fathead minnows.[26]

The red kangaroo is still an abundant species and like all Australian wildlife is protected by legislation. It has even benefited from the spread of agriculture and creation of man-made waterholes. However competition with livestock and rabbits poses a threat. It is also sometimes shot by farmers as a pest although a "destruction permit" is required from the relevant state government.

Kangaroos dazzled by headlights or startled by engine noise often leap in front of vehicles, severely damaging or destroying smaller or unprotected vehicles. The risk of harm to vehicle occupants is greatly increased if the windscreen is the point of impact. As a result, "kangaroo crossing" signs are commonplace in Australia.

The kangaroo is so numerous that there is regulated harvest of its hide and meat. Hunting permits and commercial harvesting are controlled under nationally approved management plans, which aim to maintain red kangaroo populations and manage them as a renewable resource. Harvesting of kangaroos is controversial, particularly due to the animal's popularity.[25]

In the year 2000, 1,173,242 animals were killed.[27] In 2009 the government put a limit of 1,611,216 for the number of red kangaroos available for commercial use. The kangaroo industry is worth about A$270 million each year, and employs over 4000 people.[28] The kangaroos provide meat for both humans and pet food. Kangaroo meat is very lean with only about 2% fat. Their skins are used for leather.

^Newsome, A.E. (1975). "An ecological comparison of the two arid-zone kangaroos of Australia, and their anomalous prosperity since the introduction of ruminant stock to their environment". Quarterly review of Biology50 (4): 389–424. doi:10.1086/408742. PMID1221459.